Article

Emergence of New Forms of Totally Drug-Resistant Tuberculosis Bacilli Super Extensively Drug-Resistant Tuberculosis or Totally Drug-Resistant Strains in Iran

Authors:
  • Mycobacteriology Research Center(MRC),National Research Center of Tuberculosis andLung Diseases (NRITLD)
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Abstract

The study documented the emergence of new forms of resistant bacilli (totally drug-resistant [TDR] or super extensively drug-resistant [XDR] tuberculosis [TB] strains) among patients with multidrug-resistant TB (MDR-TB). Susceptibility testing against first- and second-line drugs was performed on isolated Mycobacterium tuberculosis strains. Subsequently, the strains identified as XDR or TDR M tuberculosis were subjected to spoligotyping and variable numbers of tandem repeats (VNTR). Of 146 MDR-TB strains, 8 XDR isolates (5.4%) and 15 TDR isolates (10.3%) were identified. The remaining strains were either susceptible (67%) or had other resistant patterns (20%). Overall, the median of treatments and drugs previously received by MDR-TB patients was two courses of therapy of 15 months' duration with five drugs (isoniazid [INH], rifampicin [RF], streptomycin, ethambutol, and pyrazinamide). The median of in vitro drug resistance for all studied cases was INH and RF. The XDR or TDR strains were collected from both immigrants (Afghan, 30.4%; Azerbaijani, 8.6%; Iraqi, 4.3%) and Iranian (56.5%) MDR-TB cases. In such cases, the smear and cultures remained positive after 18 months of medium treatment with second-line drugs (ethionamide, para-aminosalicylic acid, cycloserine, ofloxacin, amikacin, and ciprofloxacin). Spoligotyping revealed Haarlem (39.1%), Beijing (21.7%), EAI (21.7%), and CAS (17.3%) superfamilies of M tuberculosis. These superfamilies had different VNTR profiles, which eliminated the recent transmission among MDR-TB cases. The isolation of TDR strains from MDR-TB patients from different regional countries is alarming and underlines the possible dissemination of such strains in Asian countries. Now the next question is how one should control and treat such cases.

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... The Cox regression model is one of the most common of these statistical approaches (1,8,(16)(17)(18). Another method is time-varying effects model, a generalization of the Cox regression model, which studies the time-dependent effects of the studied variables (15,(19)(20). The model time-varying effects allows researchers not only to study the time-dependent effects of the studied variables but also to distinguish time-independent from time-dependent variables (13,15,20). ...
... The model time-varying effects allows researchers not only to study the time-dependent effects of the studied variables but also to distinguish time-independent from time-dependent variables (13,15,20). In this method, by creating a series of interactive factors that includes the interaction between the desired variables and a function of time could fit a model for time-dependent variables (this function f (t) can be in the form of ,... , ), ln( t t t ) (15,19,20 ...
... Time-varying effects model is a method considered for studying the time-dependent effects of the studied variables (15,(19)(20). This model can identify variables with variable effects over time and allows researchers to evaluate the process of changing the effects of these variables over time (13,15,20). ...
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... The bacterial (persisters) population survives due to their ability to growth arrest during exposure to fatal antibiotic ( (Magiorakos et al. 2012;Velayati et al. 2009). The pictorial representation of the mechanism of antimicrobial agents and resistance by microbes (Vaou et al. 2021) in ( Figure 2). ...
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... Different levels of resistance are defined by the WHO: MDR TB is caused by Mtb resistant to at least isoniazid and rifampicin, the cornerstone medicines for the treatment of TB; rifampicin-resistant disease requires similar clinical management to MDR TB; pre-XDR TB is MDR TB or rifampicin-resistant TB that is also resistant to any fluoroquinolone; and XDR TB is pre-XDR TB with resistance to at least bedaquiline or linezolid 222,223 . ...
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Antimicrobial resistance poses a significant threat to the sustainability of effective treatments against the three most prevalent infectious diseases: malaria, human immunodeficiency virus (HIV) infection and tuberculosis. Therefore, there is an urgent need to develop novel drugs and treatment protocols capable of reducing the emergence of resistance and combating it when it does occur. In this Review, we present an overview of the status and underlying molecular mechanisms of drug resistance in these three diseases. We also discuss current strategies to address resistance during the research and development of next-generation therapies. These strategies vary depending on the infectious agent and the array of resistance mechanisms involved. Furthermore, we explore the potential for cross-fertilization of knowledge and technology among these diseases to create innovative approaches for minimizing drug resistance and advancing the discovery and development of new anti-infective treatments. In conclusion, we advocate for the implementation of well-defined strategies to effectively mitigate and manage resistance in all interventions against infectious diseases.
... This requires a more analytical approach to the development and testing of potential new drugs. Current treatments, such as Rifampicin, are unable to cure TB strains that are multidrug-resistant, extensively drug-resistant, or completely drug-resistant [33][34][35]. Therefore, it is of the utmost importance to create new pharmacological regimens that drastically reduce the length of time required to treat tuberculosis for both strains that are sensitive to and resistant to drug. ...
... In 2015, approximately 580,000 infections advanced to multidrug-resistant TB globally, and among them, hundreds were XDR-TB. Incidents of totally drug-resistant TB (TDR-TB) were also recorded [32,90,91]. WHO suggested that SA is included in the countries that are recording high incidents of multidrug-resistant TB in the globe and this is associated with the perceptible increase of multidrug-resistant TB cases that are recorded [89]. ...
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... Tuberculosis (TB) is a chronic infectious disease, caused mainly by Mycobacterium tuberculosis (M.tb) , it has been reported in most countries , WHO (World Health Organization) estimates that about a third world's population is infected with M.tb [1] . A serious problem to fight TB is the emergence of resistance at different levels (MDR, XDR, and XXDR-TB /TDR) [2] , the latter resist all the drugs in use and recorded in Iraq among the immigrants [3] . Therefore, there is an emergency for developing new anti-mycobacterial agents with unique mechanism of action. ...
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Tuberculosis caused by Mycobacterium tuberculosis is under an urgent need for developing new drug with new target and action , as most available drugs are ineffective due to development of drug resistance at different levels . QSAR model was built and validated to find suitable ligands for inhibition of strategic target in M. tuberculosis . Fifteen molecules were obtained, these are non-mutagenic , non-carcinogenic , non-teratogenic and satisfied the ADME requirements . They docked strongly to the candidate target LepB (Rv2903c)/Spase I, a membrane bound protein . Binding affinities were (-6 to -7.8) kcal/mol , those molecules can be synthesized easily as the synthetic accessibility not exceed 5.5 out of 10
... Since 2006, the presence of even more resistant strains of M. tuberculosis known as extensively drug-resistant (XDR)-TB has been recognized (Gandhi et al., 2006). Even more recently, a troubling situation has emerged with the characterization of M. tuberculosis strains found to be resistant to all antibiotics tested, a situation known as totally drug-resistant (TDR)-TB (Velayati et al., 2009;Udwadia et al., 2012). ...
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In the present medicine world antibiotic resistance is one of the key threats to universal health coverage. Researchers continue to work hard to combat this global health concern. Phage therapy, an age-old practice during the early twentieth century, was outshined by the discovery of antibiotics. With the advent of widespread antibiotic resistance, phage therapy has again redeemed itself as a potential alternative owing to its adeptness to target bacteria precisely. Limited side effects, the ability to migrate to different body organs, a distinct mode of action, and proliferation at the infection site, make phages a profitable candidate to replace conventional antibiotics. The progressive outcome of numerous in vitro studies and case reports has validated the clinical efficacy of phage therapy. The bright perspective of using phages to treat bacterial infections has fueled enormous medical research to exploit their potential as therapeutics. The gaps in the information about phages and the lack of consent for clinical trials is major hurdle for consideration of phage therapy. Crafting phage therapy as a reality in medicine requires a coordinated effort from different fraternities. With this review, we aim to emphasize the importance of phage therapy in modern medicine. This review explains their historical journey, basic phage biology, cross-talk with the host immunity, obstacles with phage therapy, and their possible remedies. Comprehensive data on the various significant clinical trials of phage therapy has been presented. We evaluated the efficacy of antibiotics and phage therapy in part and in combination, along with recent progress and future perspectives of phage therapy.
... It also features a low mutation rate of about 2.5 × 10 −10 /bp/day [4]. Such an organism is not expected to acquire drug resistance rapidly in response to antibiotic challenges, yet Mtb has readily evolved extensive drug resistance [5][6][7] or even total drug resistance [5,8,9], leading to untreatable tuberculosis [8]. In a study monitoring 141 tuberculosis (TB) patients suffering from infection with Mtb strains that are susceptible to second-line drugs (SLDs), acquired resistance in Mtb was observed in 19 patients (14%) [10]. ...
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Mycobacterium tuberculosis (Mtb) acquires drug resistance at a rate comparable to that of bacterial pathogens that replicate much faster and have a higher mutation rate. One explanation for this rapid acquisition of drug resistance in Mtb is that drug resistance may evolve in other fast-replicating mycobacteria and then be transferred to Mtb through horizontal gene transfer (HGT). This paper aims to address three questions. First, does HGT occur between Mtb and other mycobacterial species? Second, what genes after HGT tend to survive in the recipient genome? Third, does HGT contribute to antibiotic resistance in Mtb? I present a conceptual framework for detecting HGT and analyze 39 ribosomal protein genes, 23S and 16S ribosomal RNA genes, as well as several genes targeted by antibiotics against Mtb, from 43 genomes representing all major groups within Mycobacterium. I also included mgtC and the insertion sequence IS6110 that were previously reported to be involved in HGT. The insertion sequence IS6110 shows clearly that the Mtb complex participates in HGT. However, the horizontal transferability of genes depends on gene function, as was previously hypothesized. HGT is not observed in functionally important genes such as ribosomal protein genes, rRNA genes, and other genes chosen as drug targets. This pattern can be explained by differential selection against functionally important and unimportant genes after HGT. Functionally unimportant genes such as IS6110 are not strongly selected against, so HGT events involving such genes are visible. For functionally important genes, a horizontally transferred diverged homologue from a different species may not work as well as the native counterpart, so the HGT event involving such genes is strongly selected against and eliminated, rendering them invisible to us. In short, while HGT involving the Mtb complex occurs, antibiotic resistance in the Mtb complex arose from mutations in those drug-targeted genes within the Mtb complex and was not gained through HGT.
... To characterize bacteria that showed in vitro resistance to all tested first-and second-line medications, Velayati et al. coined the term "totally drugresistant tuberculosis" (TDR-TB) in 2009. In such instances, it is recommended to consult a specialist in infectious diseases who has experience in treating resistant strains [52]. Against these strains, which have been detected in India, Iran, Italy, and South Africa, novel tactics and medications (including delam53,anid, bedaquiline, SQ109, and sutezolid) are being tested in clinical trials at the moment [54]. ...
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Background Spinal tuberculosis (TB) is the most common extrapulmonary form of tuberculosis. In both developing and developed countries, TB has been on the rising trend due to factors such as increasing HIV coinfection, multidrug resistance of the organism, and global migration. Spinal TB, which most often affects the lower thoracic and thoracolumbar area, accounts for 50% of all musculoskeletal tuberculosis. Methods Using the Cochrane Database of Systematic Reviews, EMBASE, and PubMed, a systematic computerized literature search was performed. Analyses of studies published within the past 10 years were conducted. The searches were performed using Medical Subject Headings terms, with “spinal tuberculosis,” “diagnosis,” “epidemiology,” and “etiology”,“management,” “surgery,” and “therapy” as subheadings. Results Progressive collapse, kyphosis, and neurological deficiency are hallmarks of the disease because of its destructive effect on the intervertebral disc and adjacent vertebral bodies. The condition may be identified using laboratory testing and distinctive imaging features, but the gold standard for diagnosis is tissue diagnosis using cultures, histology, and polymerase chain reaction. Uncomplicated spinal TB is today a medical condition that can be adequately treated by multidrug ambulatory chemotherapy. Surgery is reserved for individuals who have instability, neurological impairment, and deformity correction. Debridement, deformity correction, and stable fusion are the cornerstones of surgical treatment. Conclusions Clinical results for the treatment of spinal TB are generally satisfactory when the disease is identified and treated early. However, the major health issue and the biggest obstacle in achieving the goals of the “End TB strategy” is the recent rise in the emergence of drug resistance. Hence strict vigilance and patient perseverance in the completion of the treatment is the main need of the hour.
... Il est essentiel d'élucider les caractéristiques génomiques qui peuvent expliquer l'infectivité et la transmission contrastées des lignées du complexe Mycobacterium tuberculosis (MTBC) [2][3][4], ainsi que de tenir compte de l'architecture génétique du système immunitaire de l'hôte. Les effets de la mondialisation, comme l'augmentation du nombre de patients infectés par des souches non endémiques, la propagation de souches multirésistantes (MDR) à partir de pays où les soins de santé sont insuffisants et l'expansion inquiétante de souches totalement résistantes aux médicaments (TDR), posent un défi de taille [5]. Cette situation se rencontrant également pour d'autres espèces de pathogènes humains [6,7]. ...
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... Recently, the treatment options for tuberculosis disease has become obsolete in case of XDR (extremely drug-resistant) strains as well as TDR (totally drug-resistant) strains. It is reported that the antibiotic resistance in these superbugs are due to spontaneous mutation and horizontal gene transfer has no role on it (Velayati et al., 2009). However, in many Gram-negative bacteria such as Escherichia coli, Salmonella enterica, and Klebsiella pneumonia, the evolution and transmission of antibiotic resistance happens mainly through horizontal gene transfer. ...
... The standard of care for TB, for example, is a multi-drug antibiotic regimen given over four to nine months. Importantly, Mtb strains resistant to some or all available antibiotics have emerged [5,6], including stains resistant to newly developed antibiotics such as bedaquiline, delamanid, and pretomanid [7,8], highlighting the need for novel treatment strategies for TB. Similarly, antibiotic resistance is of significant concern in infections caused by nontuberculous mycobacteria [9,10]. ...
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Infections caused by members of the mycobacterium tuberculosis complex [MTC] and nontuberculous mycobacteria [NTM] can induce widespread morbidity and mortality in people. Mycobacterial infections cause both a delayed immune response, which limits rate of bacterial clearance, and formation of granulomas, which contain bacterial spread, but also contribute to lung damage, fibrosis, and morbidity. Granulomas also limit access of antibiotics to bacteria, which may facilitate development of resistance. Bacteria resistant to some or all antibiotics cause significant morbidity and mortality, and newly developed antibiotics readily engender resistance, highlighting the need for new therapeutic approaches. Imatinib mesylate, a cancer drug used to treat chronic myelogenous leukemia [CML] that targets Abl and related tyrosine kinases, is a possible host-directed therapeutic [HDT] for mycobacterial infections, including those causing TB. Here, we use the murine Mycobacterium marinum [Mm] infection model, which induces granulomatous tail lesions. Based on histological measurements, imatinib reduces both lesion size and inflammation of surrounding tissue. Transcriptomic analysis of tail lesions indicates that imatinib induces gene signatures indicative of immune activation and regulation at early time points post infection that resemble those seen at later ones, suggesting that imatinib accelerates but does not substantially alter anti-mycobacterial immune responses. Imatinib likewise induces signatures associated with cell death and promotes survival of bone marrow-derived macrophages [BMDMs] in culture following infection with Mm. Notably, the capacity of imatinib to limit formation and growth of granulomas in vivo and to promote survival of BMDMs in vitro depends upon caspase 8, a key regulator of cell survival and death. These data provide evidence for the utility of imatinib as an HDT for mycobacterial infections in accelerating and regulating immune responses, and limiting pathology associated with granulomas, which may mitigate post-treatment morbidity.
... Recently, the treatment options for tuberculosis disease has become obsolete in case of XDR (extremely drug-resistant) strains as well as TDR (totally drug-resistant) strains. It is reported that the antibiotic resistance in these superbugs are due to spontaneous mutation and horizontal gene transfer has no role on it (Velayati et al., 2009). However, in many Gram-negative bacteria such as Escherichia coli, Salmonella enterica, and Klebsiella pneumonia, the evolution and transmission of antibiotic resistance happens mainly through horizontal gene transfer. ...
... According to WHO report on latent tuberculosis infection published on 2018, Mtb affects one third of the population of the world [12,13], resulting in two million fatalities annually [14], due to its dormancy and capability to infect during this period [13]. Multidrug-resistant, extensively drug-resistant, and completely drug-resistant TB strains do not respond to any standard treatment, therefore are not curable with current treatments including Rifampicin (RIF) [15][16][17]. The potential evolution of mycobacterial strains may evolve by deleting the cassette, it is always a concern when developing new drugs for infectious diseases. ...
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Tuberculosis (TB), an infectious disease caused by the Mycobacterium tuberculosis (Mtb), has been responsible for the deaths of millions of individuals around the globe. A vital protein in viral pathogenesis known as resuscitation promoting factor (RpfB) has been identified as a potential therapeutic target of anti-tuberculosis drugs. This study offered an in silico process to examine possible RpfB inhibitors employing a computational drug design pipeline. In this study, a total of 1228 phytomolecules were virtually tested against the RpfB of Mtb. These phytomolecules were sourced from the NP-lib database of the MTi-OpenScreen server, and five top hits (ZINC000044404209, ZINC000059779788, ZINC000001562130, ZINC000014766825, and ZINC000043552589) were prioritized for compute intensive docking with dock score ≤ − 8.5 kcal/mole. Later, molecular dynamics (MD) simulation and principal component analysis (PCA) were used to validate these top five hits. In the list of these top five hits, the ligands ZINC000044404209, ZINC000059779788, and ZINC000043552589 showed hydrogen bond formation with the functional residue Glu²⁹² of the RpfB protein suggesting biological significance of the binding. The RMSD study showed stable protein–ligand complexes and higher conformational consistency for the ligands ZINC000014766825, and ZINC000043552589 with RMSD 3–4 Å during 100 ns MD simulation. The overall analysis performed in the study suggested promising binding of these compounds with the RpfB protein of the Mtb at its functional site, further experimental investigation is needed to validate the computational finding.
... Several factors have contributed to the continuous health threat of TB globally. This includes the development of drug resistance such as multidrug-resistant tuberculosis (MDR-TB), extensively drug-resistant tuberculosis (XDR-TB) 2 , and totally drug-resistant tuberculosis (TDR-TB) 3 . One third of the world's population is thought to be infected with M. tuberculosis 4 , and new infections occur at a rate of about one per second. ...
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Mycobacterial infections and multidrug-resistant (MDR) strains of Mycobacterium generate high mortality, this has triggered the scientific community to search for novel, effective, and safer therapeutics. A series of 4, 5-disubstituted-1, 3, 4-oxadiazole derivatives were screened for mycobacterial activity against H37Rv, MDR and XDR strains. To recognize the mechanism of action of these compounds and to identify their supposed drug target, molecular docking and dynamics studies were employed against DprE1 mycobacterial enzyme, which is reported to be an essential enzyme for mycobacterial growth and survival. The ADME and drug-likeness properties revealed that all the compounds have good pharmacokinetic properties. All the compounds have high affinity towards the enzyme. The newly synthesized derivatives were confirmed through FT-IR, 1 H-NMR, and LCMS. In-vitro microplate alamar blue assay (MABA) to determine the MIC (minimum inhibitory concentration) values against Mycobacterium tuberculosis H37Rv was performed for the synthesized compounds. The synthesized compounds 2A, 3A, 4A, 5A and 6A exhibited promising activity against Mycobacterium tuberculosis.
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This review examines the impact of F420 biosynthesis protein C (fbiC) mutations in Mycobacterium tuberculosis (Mtb) and their influence on the bacterium’s dormancy mechanisms. The potential role of fbiC mutations and functional impairments in the persistence of Mtb is emphasized. Tuberculosis (TB) bacilli can enter a dormant state with minimal metabolic activity, allowing them to conserve resources and survive in low-nutrient, low-oxygen environments for extended periods. While the fbiC gene contributes to dormancy, Mtb can achieve this state through multiple genetic and metabolic pathways, suggesting that it may still undergo dormancy even with functional impairments in fbiC. In this review, we utilized several scientific databases, including PubMed, Web of Science, and Google Scholar, and set of key search terms including “fbiC gene,” “F420 Biosynthesis,” “ Mycobacterium tuberculosis ,” “Dormancy,” and “Drug Resistance” to highlight the significance of the fbiC gene in regulating dormancy and explore how Mtb compensates for fbiC dysfunction through various metabolic adaptations.
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Background The overexpression of efflux pumps (Eps) was reported to contribute to multidrug resistant tuberculosis (MDR-TB). Increases in Eps that expel structurally unrelated drugs contribute to reduced susceptibility by decreasing the intracellular concentration of antibiotics. In the present study, an association of mycobacterial membrane protein (MmpS5-MmpL5) Ep and its gene regulator ( Rv 0678) was investigated in MDR-tuberculosis isolates. Methods MTB strains were isolated from patients at two different intervals, i.e., once when they had persistent symptoms despite 3–15 ≥ months of treatment and once when they had started new combination therapy ≥2–3 months. Sputum specimens were subjected to Xpert MTB/rifampicin test and then further susceptibility testing using proportional method and multiplex polymerase chain reaction (PCR) were performed on them. The isolates were characterized using both 16S-23S RNA and hsp 65 genes spacer (PCR-restriction fragment length polymorphism). Whole-genome sequencing (WGS) was investigated on two isolates from culture-positive specimen per patient. The protein structure was simulated using the SWISS-MODEL. The input format used for this web server was FASTA (amino acid sequence). Protein structure was also analysis using Ramachandran plot . Results WGS documented deletion, insertion, and substitution in transmembrane transport protein MmpL5 ( Rv 0676) of Eps. Majority of the studied isolates ( n = 12; 92.3%) showed a unique deletion mutation at three positions: (a) from amino acid number 771 (isoleucine) to 776 (valine), (b) from amino acid number 785 (valine) to 793 (histidine), and (c) from amino acid number 798 (leucine) to 806 (glycine).” One isolate (7.6%) had no deletion mutation. In all isolates ( n = 13; 100%), a large insertion mutation consisting of 94 amino acid was observed “from amino acid number 846 (isoleucine) to amino acid number 939 (leucine)”. Thirty-eight substitutions in Rv 0676 were detected, of which 92.3% were identical in the studied isolates. WGS of mycobacterial membrane proteins (MmpS5; Rv 0677) and its gene regulator ( Rv 0678) documented no deletion, insertion, and substitution. No differences were observed between MmpS5-MmpL5 and its gene regulator in isolates that were collected at different intervals. Conclusions Significant genetic mutation like insertion, deletion, and substitution within transmembrane transport protein MmpL5 ( Rv 0676) can change the functional balance of Eps and cause a reduction in drug susceptibility. This is the first report documenting a unique amino acid mutation (insertion and deletion ≥4–94) in Rv 0676 among drug-resistant MTB. We suggest the changes in Mmpl5 ( Rv0676 ) might occurred due to in-vivo sub-therapeutic drug stress within the host cell. Changes in MmpL5 are stable and detected through subsequent culture-positive specimens.
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Background: Mycobacterium tuberculosis, which is responsible for tuberculosis, has become resistant to a majority of the existing antimicrobial treatments. As a result, effectively treating all tuberculosis patients has become challenging, and it's anticipated that cases of drug-resistant M. tuberculosis causing tuberculosis will rise globally. This emphasizes the pressing need for prompt detection and the creation of novel antimicrobial options to fight M. tuberculosis. When some germs become resistant to many medicines, it's hard to cure the infections they cause. It's important to look into different options for fighting TB. That's why studying natural plants, like garlic (Allium sativum), to learn about their safety and ability to fight microbes, including its various biological properties such as anti-tumour, anti-hyperlipidemic, and antimicrobial effects, is necessary. Allium sativum holds promise for creating new treatment options. Involving traditional healers in TB healthcare could aid in delivering garlic extracts to patients. Tuberculosis is a significant global cause of death, particularly when combined with AIDS. This contagious pulmonary disease spreads readily, especially in overcrowded and impoverished conditions. Garlic is a strong way to fight against infections from lots of different germs like bacteria, fungi and viruses. Using garlic to combat MDR-TB could have significant implications for public health.
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Excessive, arbitrary, self-medication, and misuse of antibiotics have caused widespread antibiotic resistance, but with the emergence of multiple antibiotic resistances, these concerns have increased. Efflux pumps are an important pathway involved in antibiotic resistance and can send the drug used in clinical cases out of the bacterial cell. Many studies show the role of these pumps in biofilm formation as well as increasing biofilm formation. Considering the effective relationship between antibiotic resistance from the efflux pump pathway and biofilm increase in bacteria, the purpose of this study was to investigate various aspects of the efflux pump pathway in biofilm exacerbation, especially in Mycobacterium . For this purpose, we studied more than 60 articles with keywords efflux pump, antibiotic resistance, biofilm formation, and Mycobacterium tuberculosis from valuable data sources such as PubMed, Scopus, Google Scholar, and Web of Science. Through the investigation, we came to the conclusion that the efflux pump is one of the main pathways of antibiotic resistance in bacteria, especially M. tuberculosis , which can increase the formation of biofilm in them, and as a result of this cooperation, the treatment process can become much more difficult. We suggest that all drug resistance pathways and their genes are investigated in the occurrence of other diseases, not only tuberculosis, in different geographical areas.
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Cytochrome bd (cyt-bd) oxidase, one of the two terminal oxidases in the Mycobacterium tuberculosis (Mtb) oxidative phosphorylation pathway, plays an indispensable role in maintaining the functionality of the metabolic pathway under stressful conditions. However, the absence of this oxidase in eukaryotic cells allows researchers to select it as a potential drug target for the synthesis of anti-tubercular (anti-TB) molecules. Cyt-bd inhibitors have often been combined with cytochrome bcc/aa3 super-complex inhibitors in anti-TB drug regimens to achieve a desired bactericidal response. The functional redundancy between both the terminal oxidases is responsible for this. The cryo-EM structure of cyt-bd oxidase from Mtb (PDB ID: 7NKZ) further accelerated the research to identify its inhibitor. Herein, we have summarized the reported anti-TB cyt-bd inhibitors, insight into the rationale behind targeting cyt-bd oxidase, and an outline of the architecture of Mtb cyt-bd oxidase.
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Background: Pili are polymeric, hydrophobic, proteinaceous structures generally composed of a major repeating subunit called pilin and, in some cases, a minor tip-associated adhesin subunit. Pili are involved in many virulence-associated functions, such as biofilm formation, adherence, and colonization of mucosal surfaces. Methods: Mycobacterium tuberculosis (MTB) strains were isolated from clinically and laboratory-confirmed cases of tuberculosis (TB). The TB isolates were subjected to the Xpert MTB/rifampicin test and then, further susceptibility testing was performed on them against first- and second-line drugs using proportional methods. Thereafter, the selected isolates were subculture in Dubos Tween-albumin liquid culture medium, and at their exponential growth phase (OD600 = 0.05 (5 × 106 colony-forming unit/mL), cells were observed under atomic force microscopy (AFM). For each isolate, 15-20 steel sample packs were prepared and observed under AFM. Here, the data presented are the result of average observation. Results: Under AFM, seven different types of pili were detected, out of which four types, i.e., Type III, Type IV secretion pili, and Type IV-like pili, curli-like pili (MTP) were similar to reported pili in Gram-negative and Gram-positive bacteria. Whereas the other three forms, i.e., Type V (relief funnel pili), Type VI (adhesion tapering), and Type VII (adhesion flap pili), were newly identified and named according to their appearance. Both Types of IV pili were detected in all clinical isolates irrespective of their susceptibility patterns, although significant differences were observed from the side of their protruding. Type Curli pili is similar in appearance in all clinical isolates. Types VI and VII were detected only in extensively drug-resistant and totally drug-resistant-TB isolates (100%). The Type III pili (secretion needle pili) was present in both susceptible- and drug-resistant bacilli, although in drug-resistant strains, we found a considerable difference in their length (50 μ ±10 nm in length) and sometimes, they also had tapering at end. The Type V pili was seen in susceptible isolates but it was at the resting stage (100%; lying aside of cell wall) whereas in drug-resistant isolates, they were getting apart from the cell wall of bacilli with a clear tapering or funnel shape structure. Conclusion: The results of this study highlight the importance of new types of pili expressions in respect of susceptibility patterns in TB. The identified new types of pili would be promising approaches for the treatment and prevention of drug-resistant TB, which needs further investigation.
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Background Resistance to most of the antitubercular drugs has been on rising trends due to the misuse of existing drugs. This has encouraged us to explore a novel scaffold that has the potential for quick antimicrobial action with minimum side effects. Nitrofurans have attracted us due to their extensive biological activities, such as antibacterial and antifungal activities. Objective The antitubercular activities of 126 nitrofuran derivatives have been investigated by using indicator parameters and topological and structural fragment descriptors. Methods The different quantitative structure activity relationship (QSAR) models have been created and validated by using two different methodologies: combinatorial protocol in multiple linear regression (CP-MLR) and partial least-squares (PLS) analysis. Results The 16 descriptors identified in CP-MLR are from six different classes: Constitutional, Functional, Atom Centered Fragments, Topological, Galvez, and 2D autocorrelation. Indicator parameters and Dragon descriptors suggested that the presence of a furan ring substituted by nitro group is essential for antitubercular activity. Further descriptors from constitutional, and functional classes suggest that the number of double bonds, number of sulphur atoms and number of fragments like thiazole, morpholine and thiophene should be minimum, along with the positive influence of Kier-Hall electrotopological states (Ss) for improved activity. The ACF class descriptors, GALVEZ class descriptors, and 2D-AUTO descriptor GATS4p have also shown positive influence on the antitubercular activity. The TOPO class descriptor T(O…S) suggests that the minimum gap between sulphur and oxygen is favorable for activity. Conclusions The models acknowledged in the study have explained the variance between 72 to 76% in the training set and in the prediction of the test set compounds. Also, compounds 122, 123 and 82 were found to possess good binding affinity towards nitroreductase.
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According to the World Health Organization (WHO), tuberculosis (TB) remains one of the top 10 causes of death worldwide. Tuberculosis is a major global health threat. In 2022, an estimated 10 million people worldwide developed TB disease, and there were about 1.5 million TB-related deaths. TB primarily affects low- and middle-income countries, with the highest burden in Africa, Asia, and the Western Pacific regions. The WHO has launched the "End TB Strategy" with the aim of eliminating TB as a public health problem by 2035. Early diagnosis and prompt initiation of treatment are essential for effective TB control. WHO recommends a package of interventions known as "Directly Observed Treatment, Short-course" (DOTS) for TB control, which includes standardized diagnostic approaches, access to quality-assured drugs, and supportive treatment adherence measures. Tuberculosis (TB) remains a global health burden, necessitating the development of new therapeutic strategies. Fluoroquinolones (FQs) have emerged as promising agents in the treatment of TB due to their potent antimicrobial activity against Mycobacterium tuberculosis (Mtb) and their ability to penetrate intracellular compartments. This review aims to summarize the current knowledge on the use of FQs as antitubercular agents, highlighting their mechanisms of action, efficacy and limitations.
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Tuberculosis (TB) is a major global health problem and the second most prevalent infectious killer after COVID-19. It is caused by Mycobacterium tuberculosis ( Mtb ) and has become increasingly challenging to treat due to drug resistance. The World Health Organization declared TB a global health emergency in 1993. Drug resistance in TB is driven by mutations in the bacterial genome that can be influenced by prolonged drug exposure and poor patient adherence. The development of drug-resistant forms of TB, such as multidrug resistant, extensively drug resistant, and totally drug resistant, poses significant therapeutic challenges. Researchers are exploring new drugs and novel drug delivery systems, such as nanotechnology-based therapies, to combat drug resistance. Nanodrug delivery offers targeted and precise drug delivery, improves treatment efficacy, and reduces adverse effects. Along with nanoscale drug delivery, a new generation of antibiotics with potent therapeutic efficacy, drug repurposing, and new treatment regimens (combinations) that can tackle the problem of drug resistance in a shorter duration could be promising therapies in clinical settings. However, the clinical translation of nanomedicines faces challenges such as safety, large-scale production, regulatory frameworks, and intellectual property issues. In this review, we present the current status, most recent findings, challenges, and limiting barriers to the use of emulsions and nanoparticles against drug-resistant TB.
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The success of the TB control program is hampered by the major issue of drug-resistant tuberculosis (DR-TB). The situation has undoubtedly been made more difficult by the widespread and multidrug-resistant (XDR) strains of TB. The modification of existing anti-TB medications to produce derivatives that can function on resistant TB bacilli is one of the potential techniques to overcome drug resistance affordably and straightforwardly. In comparison to novel pharmaceuticals for drug research and progress, these may have a better half-life and greater bioavailability, be more efficient, and serve as inexpensive alternatives. Mycobacterium tuberculosis, which is drug-susceptible or drug-resistant, is effectively treated by several already prescribed medications and their derivatives. Due to this, the current review attempts to give a brief overview of the rifampic-in derivatives that can overcome the parent drug's resistance and could, hence, act as useful substitutes. It has been found that one-third of the global population is affected by M. tuberculosis. The most common cause of infection-related death can range from latent TB to TB illness. Antibiotics in the rifamycin class, including rifampicin or rifampin (RIF), rifapentine (RPT), and others, have a special sterilizing effect on M. tuberculosis. We examine research focused on evaluating the safety, effectiveness, pharmacokinetics, pharmacodynamics, risk of medication interactions, and other characteristics of RIF analogs. Drug interactions are especially difficult with RIF because it must be taken every day for four months to treat latent TB infection. RIF continues to be the gold standard of treatment for drug-sensitive TB illness. RIF's safety profile is well known, and the two medi-cines' adverse reactions have varying degrees of frequency. The authorized once-weekly RPT regi-men is insufficient, but greater dosages of either medication may reduce the amount of time needed to treat TB effectively.
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Background Pili producing genes in different life cycles of Mycobacterium tuberculosis ( M. tuberculosis ) were assessed. M. tuberculosis has two life cycles: dormant and active states. We aimed to assess the pili producing genes such as curli pili of M. tuberculosis (mtp) encoded by the mtp gene (Rv3312A) and fimbrial low-molecular-weight protein encoded by flp gene (Rv3656c) which were compared and analyzed. Methods Two hundred M. tuberculosis isolates were investigated both at active and dormant states for production and expression of pili. The dormant M. tuberculosis was achieved by incubation in a sealed tube (modified Wayne method). The susceptibility of M. tuberculosis was evaluated on genes, rpob, inh, katg, and gyra by using multiplex polymerase chain reaction (PCR) and single-strand conformational polymorphism methods. The PCR–restriction fragment length polymorphism was used to express pili genes mtp and flp and then the PCR products was digested using restriction enzyme Fnu4HI, XmaI, and MspJI and AciI, TagII, and HaeII, respectively. The transmission electron microscopy was also used to detect pili in different isolates. The result was compared and analyzed using H37RV as a gold standard. Results The mtp and flp PCR products were 263 and 122 bp in the studied strains irrespective of M. tuberculosis different life cycles, respectively. The PCR products were analyzed on 8% Polyacrylamide gel electrophoresis (PAGE), and in the 180/200 (20%), producing five fragments of 25,40,45,63,90 bp with the Fun4HI and two fragments of 126,138 bp with the XmaI and uncut with the MspJI for mtp gen were obtained at the dormant and active states of M. tuberculosis ( P < 0.05). Similarly in flp gene producing three fragments of 22,35,65 bp with AciI and two fragments of 35.87 bp with TagII and two fragments of 38.84 bp with HaeII were obtained (P < 0.05). In contrast to genotyping analysis, the electron microscopy examination showed protruding of pili from M. tuberculosis , especially in dormant mycobacterium (15/100; 15%), that was multidrug resistance and extensive drug resistance isolates ( P > 0.05). Conclusion Pili were shown by electron microscopy, although at the gene expression, the insignificant difference was observed at the dormant strains in comparison to active states. Therefore, we may conclude that other genes might be involved in pili production of M. tuberculosis that needs further investigation. Although, the resistance phenomena might influence the pili producing gene expression that showed in our results.
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Mycobacterium tuberculosis drug resistance is emerging and new drug targets are needed. Tryptophan biosynthesis is necessary for M. tuberculosis replication and virulence. Indole-3-glycerol phosphate synthase (IGPS) catalyzes a step in M. tuberculosis tryptophan biosynthesis and has been suggested as a potential anti-infective target, but our understanding of this enzyme is limited. To aid in inhibitor design and gain a greater mechanistic picture of this enzyme, there is a need to understand the roles of active site amino acids in ligand binding and catalysis. In this work, we explored the roles of conserved active site amino acids Glu57, Lys59, Lys119, Glu168, and Glu219. Mutation of each to Ala results in loss of all detectable activity. The Glu57Gln, Lys59Arg, Lys119Arg, Glu168Gln, and Glu219Asp mutations result in large activity losses, while Glu219Gln has enhanced activity. Analysis of the enzymatic data yields the following main conclusions: (A) Lys119 is the likely catalytic acid in the CdRP ring closure step. (B) Glu168 stabilizes a charged reaction intermediate and may also be the catalytic base. (C) Glu57, Glu219, and Lys119 form a closely arranged triad in which Glu57 and Glu219 modulate the pKa of Lys119, and thus overall activity. This increased understanding of inter- and intramolecular interactions and demonstration of the highly coordinated nature of the M. tuberculosis IGPS active site provide new mechanistic information and guidance for future work with this potential new drug target.
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Tuberculosis or TB is an airborne contagious disease becoming an increasing global health issue day by day. The chief cause of TB is bacterial complex of Mycobacterium tuberculosis (MTB). Subsequently, evolution of totally drug resistant (TDR) strains of also creates a serious health challenge leading to the need of discovering new drugs for the treatment of TB with novel mechanisms of action. From ancient times natural remedies originating from both plants and microbes are being used as potent sources of antimicrobial remedies. These natural products are rich in chemical diversity and such remedies are being validated through centuries of evolution. Therefore, present study includes in silico screening of the potent ligands from Adhatoda vasica Nees, belonging to the family Acanthaceae, a well-known plant-based drug extensively used in the Ayurvedic and Unani medicine system in India for more than 2000 years. In this study 39 molecules of A. vasica are docked against the target protein Glutamine synthatase. Out of which 25 favorable conformations were selected. Only 12 molecules could pass the Lipinski’s filter. Further analysis of the ligand receptor compound suggested five potential biomolecules, viz., 3-hydroxyanisotine, Vasnetine, Apigenin, 2-naphthalenemethanol and l-vasicinone are to be considered as potent candidates for in vitro and in vivo tests against the target protein.KeywordsIn silicoTuberculosisMTBGlutamine synthetase Adhatoda vasica
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This book offers an integrated review of the most recent trends in natural products drug discovery and key lead candidates that are outstanding for their chemistry and biology as a starting point in novel drug development. The authors focus on different trends that are and will continue to be impacting multiples stages of modern drug discovery from NPs that have not been included in other works. This is complemented with a series of case studies from leading experts from industry and academia on key molecules and derivatives that have been chosen for their novelty in chemistry, biology and clinical applications. The book intends to reflect the current confluence of different disciplines in chemical biology and synthetic chemistry supported by a more profound knowledge of systems biology that ensures the concurrency and synergisms of expertise from different research fields that impact in the discovery of novel molecules. In the first section the chapters reflect recent approaches to exploit the biosynthetic potential of microbial resources (including genome mining, metagenomic and epigenetic approaches), as well as biosynthetic chemistry tools to respond to product supply and novel screening alternatives that have lead to the discovery of novel chemistry. The second part reviews, in the form of case studies, some examples of bioactive molecules in the important therapeutic areas of antiinfectives, oncology and antiparasitics.
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Tuberculosis is the leading bacterial killer worldwide. 8-Nitro-4H-benzo[e][1,3]thiazin-4-ones are a potent class of antitubercular agents with a new mechanism of action. BTZ043 and PBTZ169 (macozinone) have progressed to clinical studies. Herein, we give a comprehensive account of this important class of potential new drugs to treat tuberculosis. We present an overview of recent developments in the field of antitubercular benzothiazinones (BTZs) and summarize our own contributions. The review covers synthesis, structures and reactivity, mechanism of action, in vitro activity and structure activity relationships (SARs), physicochemical and pharmacokinetic properties as well as a brief summary of in vivo models and clinical studies. We address bioavailability issues and the challenge of the potentially toxic nitroaromatic moiety, including reactivity towards nucleophiles in vivo and highlight possible directions of further research into BTZs through chemical modification.
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DNA fingerprinting of Mycobacterium tuberculosis has been shown to be a powerful epidemiologic tool. We propose a standardized technique which exploits variability in both the number and genomic position of IS6110 to generate strain-specific patterns. General use of this technique will permit comparison of results between different laboratories. Such comparisons will facilitate investigations into the international transmission of tuberculosis and may identify specific strains with unique properties such as high infectivity, virulence, or drug resistance.
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#### Summary points Antituberculosis drug resistance is increasing both in the United Kingdom and internationally.1 2 It has come to greater public attention with the emergence of extensively drug resistant tuberculosis (box 1) in South Africa, where an outbreak proved rapidly fatal among people with advanced HIV infection.3 In this article we review recent global and UK trends in drug resistant tuberculosis and summarise its diagnosis, treatment, and control. Few data are available from randomised controlled trials to guide treatment of drug resistant tuberculosis, and none for multidrug resistant tuberculosis; this review is based primarily on data from observational epidemiological studies and on national and international guidelines. #### Box 1 Definitions relating to tuberculosis and drug resistance
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Relapse of tuberculosis (TB) may develop as the result of reactivation of the endogenous primary infection, or as a result of a exogenous reinfection. This survey evaluated the rate of reactivation versus recent transmission among Iranian and Afghan relapse cases. The sputum specimens were digested, examined microscopically for acid-fast bacilli, and inoculated into Löwenstein-Jensen slants by standard procedures. Thereafter, the susceptibility and identification tests were performed on culture positive specimens. Subsequently, the strains that were identified as Mycobacterium tuberculosis (258 isolates) were subjected to IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping. Additional patient's information was collected for further epidemiological analysis. Patients whose isolates had identical genotyping patterns were considered a cluster with recent transmission episode. Out of 258 available isolates, 72(28%) had multi-drug resistant (MDR-TB) in ratio and 42 (16.2%) had other resistant. Notably, 38 of MDR-TB cases (52%) were isolated from Afghan patients. By IS6110-RFLP typing method, 65 patients (25%) were clustered in 29 clusters. In cluster cases, the intra-community transmissions between Iranian and Afghan patients were 41%. All MDR-TB patients in clusters had either Haarlem I or Beijing characteristic. The risk factors like sex, family history, close contact, living condition, PPD test result and site of TB infection were not associated with clustering. Although, the MDR-TB strains were more frequent in non-cluster cases (31%) than cluster one(18%) (P < 0.05). Majority of M. tuberculosis strains isolated from non-cluster cases were belong to EAI3 (51; 30%) and CASI(32;18.6%) superfamilies. During the studied period, reactivation of a previous infection remain the more probable cause of recurrence. Although, the evidence of intra- community transmission between Iranian and Afghan TB cases, highlighted the impact of afghan immigrants in national tuberculosis control program (NTP) of Iran.
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The Direct Repeat locus of the Mycobacterium tuberculosis complex (MTC) is a member of the CRISPR (Clustered regularly interspaced short palindromic repeats) sequences family. Spoligotyping is the widely used PCR-based reverse-hybridization blotting technique that assays the genetic diversity of this locus and is useful both for clinical laboratory, molecular epidemiology, evolutionary and population genetics. It is easy, robust, cheap, and produces highly diverse portable numerical results, as the result of the combination of (1) Unique Events Polymorphism (UEP) (2) Insertion-Sequence-mediated genetic recombination. Genetic convergence, although rare, was also previously demonstrated. Three previous international spoligotype databases had partly revealed the global and local geographical structures of MTC bacilli populations, however, there was a need for the release of a new, more representative and extended, international spoligotyping database. The fourth international spoligotyping database, SpolDB4, describes 1939 shared-types (STs) representative of a total of 39,295 strains from 122 countries, which are tentatively classified into 62 clades/lineages using a mixed expert-based and bioinformatical approach. The SpolDB4 update adds 26 new potentially phylogeographically-specific MTC genotype families. It provides a clearer picture of the current MTC genomes diversity as well as on the relationships between the genetic attributes investigated (spoligotypes) and the infra-species classification and evolutionary history of the species. Indeed, an independent Naïve-Bayes mixture-model analysis has validated main of the previous supervised SpolDB3 classification results, confirming the usefulness of both supervised and unsupervised models as an approach to understand MTC population structure. Updated results on the epidemiological status of spoligotypes, as well as genetic prevalence maps on six main lineages are also shown. Our results suggests the existence of fine geographical genetic clines within MTC populations, that could mirror the passed and present Homo sapiens sapiens demographical and mycobacterial co-evolutionary history whose structure could be further reconstructed and modelled, thereby providing a large-scale conceptual framework of the global TB Epidemiologic Network. Our results broaden the knowledge of the global phylogeography of the MTC complex. SpolDB4 should be a very useful tool to better define the identity of a given MTC clinical isolate, and to better analyze the links between its current spreading and previous evolutionary history. The building and mining of extended MTC polymorphic genetic databases is in progress.
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This survey identified the spoligopatterns of Mycobacterium tuberculosis strains with an international designation responsible for transmission and prevalence of TB (2000 to 2005) among native and immigrant populations of Tehran. The spacer oligonucleotides typing was performed on 1742 Mycobacterium tuberculosis strains isolated from verified cases of TB. Clinical and demographic data of patients were collected using traditional methods. A total of 133 distinct spoligopatterns was observed. 1679 clinical isolates were clustered in 70 clusters (52.5%) and 63 isolates were defined as orphans pattern (47.3%). Based on an international spoligotype database, the east African-Indian (EAI, 24%), central Asian (CAS, 20.8%), T clade (20.7%), Haarlem I (4.4%), Beijing (3.2%) and shared type 253 (3.1%) were the major identified M. tuberculosis superfamilies. Our results showed that the intra-community TB transmission was 13.7%, whereas the inter-community transmission was 39.3% for Afghanis and 20.3% for Iranians. The study highlighted the epidemic potential of specific genotypes (EAI, CAS, T clades) among tuberculosis cases in the Tehran territory. We also confirmed that the impact of transmission through immigration is low.
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The global number of incident cases of multidrug-resistant (MDR) tuberculosis (TB) in 2000 was estimated to be 272,906 (95% confidence interval [CI], 184,948-414,295). For accurate planning of TB control programs, this estimate and others have been revised using data from additional countries and by including in the model previously treated TB cases, which had not been accounted for in the previous analysis. Multiple logistic regression was used to identify variables that were predictive of MDR-TB frequency among new and previously treated cases surveyed in 90 and 77 countries, respectively. These variables were then used to estimate MDR-TB frequencies in countries that had not been surveyed. The total number of MDR-TB cases estimated to have occurred worldwide in 2004 is 424,203 (95% CI, 376,019-620,061), or 4.3% (95% CI, 3.8%-6.1%) of all new and previously treated TB cases. In the same year, 181,408 (95% CI, 135,276-319,017) MDR-TB cases were estimated to have occurred among previously treated TB cases alone. Three countries--China, India, and the Russian Federation--accounted for 261,362 (95% CI, 180,779-414,749) MDR-TB cases, or 62% of the estimated global burden. These updated sets of estimates incorporating previously treated TB cases call for an urgent plan to expand appropriate diagnostic and treatment services for patients with MDR-TB in low-resource settings.
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Extensively drug-resistant (XDR) tuberculosis (TB) is a cause of concern, because it renders patients untreatable with available drugs. In this study, we documented the existence and transmission of XDR TB among patients with multidrug-resistant TB. These patients were referred to the National Research Institute of Tuberculosis and Lung Diseases (Tehran, Iran) for treatment and diagnosis from 2003 to 2005. The sputum specimens from a total of 2030 patients with TB were digested, examined microscopically for acid-fast bacilli, and inoculated into Lowenstein-Jensen slants by standard procedures. Testing of susceptibility to first-line drugs was performed for 1284 Mycobacterium tuberculosis isolates. Subsequently, the strains that were identified as multidrug-resistant M. tuberculosis (113 isolates) were subjected to susceptibility testing for second-line drugs. Spoligotyping and restriction fragment-length polymorphism were performed for strains that were identified as XDR M. tuberculosis. A total of 12 (10.9%) of 113 multidrug-resistant M. tuberculosis strains were resistant to all 8 second-line drugs tested and, therefore, were denoted as XDR M. tuberculosis. Retrospective analysis of the cases of XDR TB showed that all of them belonged to 1 of 2 epidemiological clusters, either a single-family cluster (4 cases) or a cluster of close contacts (8 cases). The strains were identified as belonging to the M. tuberculosis superfamilies Haarlem 1 and East African Indian 3. The emergence of XDR TB cases in Iran highlights the need to reinforce the Iranian TB policy with regard to control and detection strategies.
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To determine the drug resistance pattern to first line antituberculous drugs in National Research Institute of Tuberculosis and Lung Disease and to compare resistant rates with previous studies. An anterograde cross-sectional study was performed. The study includes all adults with documented pulmonary tuberculosis (TB) that were hospitalized in National Research Institute of Tuberculosis and Lung Disease in Tehran, from June 2003 to September 2004. Demographic characteristic, TB categories, and drug susceptibility test results were recorded. Two previous studies regarding drug susceptibility in Iran were selected as historical controls. One hundred and ninety-six new cases and 68 previously treated patients were enrolled in the study. The strains of 61% of new patients and 21% of previously treated patients were fully sensitive to all drugs. The most common resistance was streptomycin (27%) followed by isoniazid (23%) in new cases. Multiple drug resistant strains were noted in 2.6% (95% CI 0.8% to 5.8%) of new cases versus 56% (95% CI 43% to 68%) in previously treated group. The frequency of primary drug resistance to isoniazid was 9.8%-15% or streptomycin 9.8%-13% in the previous studies (p<0.00001). While these rates may not reflect the true prevalence of drug resistance on a national scale, it does partially demonstrate some defects in the existing tuberculosis control program. The significant increase of isoniazid and streptomycin resistance in the last few years would present a serious challenge to effective management of TB.
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Multi drug resistance of Mycobacterium tuberculosis (M. tuberculosis) remains a major threat to public health, reinforced by recent reports about the clinical course of patients infected with extensively drug resistant (XDR) strains in South Africa. There is little information about the clinical course of XDR tuberculosis patients in industrialised countries. We evaluated all isolates of M. tuberculosis, in which drug susceptibility testing was performed at our institution since 1997, for multi and extensive drug resistance. Clinical courses of patients infected by strains fulfilling the recently revised criteria for XDR tuberculosis were analysed. Four XDR M. tuberculosis isolates were identified. All patients had immigrated to Germany from Russia, Georgia, and former Yugoslavia and none were infected by the human immunodeficiency virus. All patients where treated for tuberculosis for 5.5 to 15 years and for XDR tuberculosis for 1.9 to 2.5 years. They received inhospital treatment in Germany for 11 months, 4.5 years and twice for 6 years. Non-compliance was an important factor in all four patients, three patients had to be treated in Germanys only locked facility for tuberculosis treatment. One patient with XDR tuberculosis died, one patient had still open pulmonary tuberculosis at last contact and 2 patients were cured. Cases of XDR tuberculosis have been treated in our region for several years. Even in a high income setting, XDR tuberculosis has a tremendous impact on quality of live, outcome and the total cost. All reasonable efforts to prevent the spread of XDR tuberculosis must be made and maintained.
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To explore mechanisms by which drug resistance might arise as a result of poor compliance during short course chemotherapy. Four theoretical mechanisms are first described. Examples of the way the mechanisms probably operate are taken from: 1) a study of once-weekly chemotherapy with streptomycin and isoniazid, and 2) the pattern of drug susceptibility in cultures from patients who relapsed after the end of treatment. Good compliance is vitally important. The value of a fourth drug in the initial phase of chemotherapy in preventing resistance is questioned. An explanation for mono-resistance to rifampicin in patients with the acquired immune deficiency syndrome (AIDS) is suggested.
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Genetic loci containing variable numbers of tandem repeats (VNTR loci) form the basis for human gene mapping and identification, forensic analysis and paternity testing. The variability of bacterial tandem repeats has not been systematically studied. Eleven tandem repeat loci in the M. tuberculosis genome were analysed. Five major polymorphic tandem repeat (MPTR) loci contained 15-bp repeats with substantial sequence variation in adjacent copies. Six exact tandem repeat (ETR) loci contained large DNA repeats with identical sequences in adjacent repeats. These 11 loci were amplified in 48 strains to determine the number of tandem repeats at each locus. The strains analysed included 25 wild-type strains of M. tuberculosis, M. bovis, M. africanum and M. microti and 23 substrains of the attenuated M. bovis BCG vaccine. One of the five MPTR loci and all six ETR loci had length polymorphisms corresponding to insertions or deletions of tandem repeats. Most ETR loci were located in intergenic regions where copy number may influence expression of downstream genes. Each ETR locus had multiple alleles in the panel. Combined analysis identified 22 distinct allele profiles in 25 wild-type strains of the M. tuberculosis complex and five allele profiles in 23 M. bovis BCG substrains. Allele profiles were reproducible and stable, as demonstrated by analyses of multiple isolates of particular reference strains obtained from different laboratories. VNTR typing may be generally useful for strain differentiation and evolutionary studies in bacteria.
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This survey identified the spoligopatterns of Mycobacterium tuberculosis strains with an international designation responsible for transmission and prevalence of Multi-Drug Resistance Tuberculosis (MDR-TB) among native and immigrant population of Tehran (2000-2005). The spacer oligonucleotides typing was performed on 263 M. tuberculosis strains isolated from verified cases of MDR-TB. Clinical and demographical data of patients were collected using traditional methods. Classical epidemiological investigation revealed that out of 263 MDR-TB cases, 175, 66.5% were isolated from Afghan immigrants. In both communities, majority of MDR-TB cases had either previous history of TB (107, 40.6%) or had a close contact (84, 31.9%). By spoligotyping, 27 distinct patterns were observed, 253 clinical isolates were grouped in 17 clusters (62.9%) and 10 isolates displayed an orphan pattern (37%). Based on an international spoligotype database, Haarlem I (85, 33.5%), Beijing (52, 20.5%), Central Asia (32, 12.1%), and EAI (21, 8.3%) were the major identified super families. Although, 76.9% of the Beijing genotypes and 100% of ST(253) strains (that was prevalent through former Soviet Union) were isolated from Afghan patients only. The linkage patterns between 30 Iranian and Afghan patients were observed. The study highlighted the epidemic potential of Haarlem I and Beijing genotypes among MDR-TB cases in Tehran territory.
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The World Health Organization has issued new guidance on the treatment of patients with extensively drug resistant tuberculosis (XDR-TB), after it was suggested that people may need to be involuntarily detained to prevent a virtually untreatable disease from emerging. Writing in the latest edition of PLoS Medicine (2007;4:e50, doi: 10.1371/journal.pmed.0040050), Jerome Singh, from South Africa's Centre for the Aids Programme of Research, recommends that the South African government follow the example of New York state in the 1990s, where forced confinement was used successfully to contain an outbreak of multiple drug resistant tuberculosis. The outbreak of XDR-TB in South Africa ( BMJ 2006;333:566, 16 Sep) has so far caused 74 …